Various ways have heretofore been proposed for chemically reacting molecules with a metal substrate in an electrochemistry cell. In some cases, the prior methodology allows molecules to be bonded strongly enough so that they can be imaged in a scanning tunnelling microscope (STM) or in .[.the.]. .Iadd.an .Iaddend.atomic force microscope (AFM). However, in the case of negatively charged molecules, such as DNA, it is extremely difficult to get them to adhere to an electrode because most metal surfaces are intrinsically negatively charged and, as such, repel the molecule. Thus a clear need exists for new and improved technology for the potentiostatic preparation of negatively charged .[.molecules.]. .Iadd.molecular .Iaddend.adsorbates such as DNA to enable them to be properly bonded to .Iadd.a .Iaddend.suitable substrate so .Iadd.that .Iaddend.they can be imaged in .Iadd.a .Iaddend.scanning tunnelling microscope .[.(STM).]. or .Iadd.an .Iaddend.atomic force .[.microscopes (AFM).]. .Iadd.microscope.Iaddend.. It is .[.toward.]. .Iadd.to .Iaddend.this end that the present invention is directed.